A wireless remote operation system including a server and a client has been widely used in enterprises. The “remote desk-top” proposed by Microsoft Inc. is one of them. A conventional wireless remote operation system represented by the “remote desk-top” is described hereinafter with reference to FIG. 12, FIGS. 13-16.
FIGS. 12A and 12B show structures of the conventional wireless remote operation system. FIG. 12A shows a structure of server 101, and FIG. 12B shows a structure of hardware at client.
First, the hardware structure of the server is described. In server 101, central processing unit 102 controls the overall server.
First memory 103, in general uses DRAM and works as a main memory for storing data. Second memory 104, in general, uses a hard-disc and works as an external memory for storing an OS and applications. Third memory 105 uses replaceable recording media such as a compact disc (CD) or a digital versatile disc (DVD) and works as a sub-memory for storing picture data and music data.
Display 106 displays an on-screen control panel or processed data on a cathode ray tube (CRT) or a liquid crystal display (LCD). Communicator 107 communicates with the outside through a modem or local area network (LAN) board. Radio section 108 communicates with client 121 by radio.
Input controller 109 controls input devices such as a keyboard and a mouse coupled to controller 109. Moving-picture generator 110 generates moving pictures, and audio-output section 111 reproduces audio-data through a speaker. Power supply 112 powers respective elements of server 101. Power switch 113 turns power-supply 112 on or off. Bus 114 includes and power lines coupling the foregoing elements with each other.
Next, the hardware structure of client 121 is described. CPU 122 controls an overall operation of client 121. Display 123 displays a picture on a CRT or an LCD. Radio section 124 communicates with radio section 108 of server 101 via radio communication route.
Both of radio-sections 108 and 124 of server 101 and client 121 use a communication method in accordance with the allowing standard as a protocol: e.g., IEEE802.11a having max. transfer rate of 54 MB/sec in 5 GHz band or IEEE802.11b having max. transfer rate of 11 MB/sec in 2.5 GHz band.
Input controller 125 controls input devices such as a keyboard and a mouse coupled to controller 125. Audio-output section 126 reproduces audio-data supplied from server 101 through a speaker. Power supply 127 powers respective elements of client 121 to work properly. Power switch 128 turns power-supply 127 on or off: Bus 129 includes signal-lines and power lines coupling the foregoing elements with each other.
An operation of the conventional wireless remote operation system is described with reference to FIGS. 13-16. FIG. 13 illustrates a displaying operation by the server alone in the conventional wireless remote operation system. Displaying the data of application software 131 is described hereinafter. This application software 131 handles both of the data of audio-accompanying moving picture which has a data-format unique to each application software, and the data of operation-related audio and display which has a data format common to the system.
The common data format of data 132 of operation-related audio and display largely depends on the hardware so that the hardware can be operated with ease. The audio data-format generally uses the pulse code modulation (PCM) format. The display data-format generally uses the RGB format that displays each one of pixels of a picture with an intensity of three primary colors, ie., red (R), green (G) and blue (B).
Application software 131 outputs data 132 of operation-related audio and display directly to video-audio reproducing block 138. Data 133 of audio-accompanying moving-picture supplied from software 131 is converted by video-audio conversion-into-common-format block 134 into data 137 of video-audio in common format, then id to video-audio reproducing block 138.
Conversion-into-common-format block 134 has independent decoding modules corresponding to the respective unique formats in order to receive audio-accompanying moving picture data in a unique format and to convert the data of audio and video into those in the common format within the system.
Video-audio reproducing block 138 reproduces the data of video-audio supplied in the common format, and outputs video data 139 on display 106 as well as audio data 140 to audio-output section 111.
In the case of displaying moving pictures, operation-related background picture 106b, which shows buttons for reproducing back or halting the moving pictures, and moving picture 106c are displayed on display screen 106a of display 106. Output sound 111a supplied from audio-output section 111 includes operation-related sound 111b such as alarm for user's operation-error and moving-picture related sound 111c such as background music and voice accompany the moving picture.
FIG. 14 illustrates a remote displaying operation in the conventional wireless remote operation system. Application software 131 of server 101 outputs data 132 of operation-related audio and display directly to video-audio converting bloc 141 used for remote operation. Data 133 of audio-accompanying moving-picture supplied from application software 131 is converted by video-audio conversion-into-common-format block 134 into video-audio data 137 in common-format, then fed into video-audio converting block 141 to be used or remote operation.
Video-audio converting block 141 converts video-audio data 137 in the common format and operation-related audio-display data 132 into video-audio data 142 for remote operation and transmitted between server 101 and client 121, and outputs data 142 to remote control block 143.
Remote control block 143 of server 101 includes a coupling status monitor, a radio communicator, and a command analyzer, although those elements are not shown in FIG. 14. The coupling-status monitor monitors the coupling statuses in client 121. The radio communicator transmits and receives commands and display data to and from client 121. The command analyzer analyzes the command supplied from client 121 and starts an application of server 101. Remote control block 143 of server 101 transmits video-audio data 142 used for remote operation to client 121 via radio section 108.
Remote control block 145 of client 121 receives data 146 of video-audio used for remote operation from server 101 via radio section 124 and outputs it to video-audio reproducing block 147 used for remote operation Block 147 reproduces data 146 supplied.
The video data for remote operation out of output 148 is output on display 123 and displayed as displayed-picture 123a on which operation-related around picture image 123b, moving-picture image 123c are superimposed. Audio data for remote operation out of output 148 is output to audio output section 126, and reproduced as output sound 126a on which operation-related 126b and picture-related sound 126c are superposed.
The foregoing video and audio are included in output 148, thus the data amount of output 148 is so huge. FIG. 15 details the operation of the server in the conventional wireless remote operation system.
Application software 131 outputs data 133 of audio-accompanying moving picture in a format unique to respective applications to audio-accompanying video data separating block 134a of video-audio conversion-into-common-format block 134. Block 134a separates data 133 into audio data 135 in its original format and video data 136 in its original format, and outputs audio data 135 to audio-data conversion-into-common-format block 134b, and outputs video data 136 to video-data converting-into-common-format block 134c. 
Converting block 134b converts audio data 135 into PCM audio data 137a, and outputs it to audio data converting block 141a of video-audio converting block 141. Video-data converting-into-common-format block 134c converts video-data 136 in the original format into video data 137b in RGB format or YUV format as the common format, and outputs it to video-data converting block 141b. Selection of RGB or YUV format as the common format can be done with format control signal 144 supplied from block 141b. 
Audio-data converting block 141a synthesizes operation-related audio data 132a in PCM format and audio data 137a in PCM format, and converts the synthesized data into audio data 142a to be used for remote operation in PCM format, then output converted audio data 142a to remote control block 143. Audio data 142a is transmitted by radio to client 121.
Video-data converting block 141b synthesizes operation-related display data 132b in RGB format and video-data 137b in RGB format, and converts the synthesized data into video data 142b in RGB format to be used for remote operation, then outputs data 142b to remote control block 143 of the server. Data 142b is transmitted to client by radio. Block 143 of server 101 synthesizes audio data 142a in PCM format and video data 142b in RGB format, and transmits the synthesized data to client 121 by radio as video-audio data to be used for remote operation.
FIG. 16 details the operation done by client 121 in the conventional wireless remote operation system. Remote control block 145 separates the video-audio data for remote operation supplied from server 101 into audio data 146a for remote operation in PCM format and video data 146b or remote operation in RGB format. Block 145 outputs audio data 146a to audio reproducing block 147a of video-audio reproducing block 147 to be used or remote operation as well as outputs video data 146b to video reproducing block 147b. 
Audio reproducing block 147a reproduces audio data 146a, and outputs audio data 148a to audio output section 126. Video reproducing block 147b reproduces video data 146b, and outputs video data 148b in RGB format to display 123.
In this conventional wireless remote operation system, when moving pictures are transmitted to the client from the server, an amount of data to be transmitted is so huge that the present transmission bandwidth is sometimes not enough to carry the data. At the client, the data amount received is so huge that the moving pictures sometimes cannot be reproduced smoothly.
Further, picture data of huge amount and audio-data of small amount are separately transmitted, so that a time difference happens between the picture data and the audio data because the picture data needs more time to process than the audio data corresponding to the picture data.
The conventional wireless remote operation system is largely influenced by whether or not a data format of moving picture and a compression method are on public view, and the presence of private formats possibly prevents a unified system from being established.